Many types of single-use syringes have been proposed. The more practical proposals generally require some mechanical operation/moving parts. A further disadvantage of known such syringes is that, whatever means is used to block the flow of liquid to the needle point, it is often possible for a determined person to remove that means. Further, even if reuse is prevented, accidental breaking of the skin with the used needle is still possible. This is a major problem for doctors and hospital staff who need especial protection from contaminated syringes.